Materials have been dyed and colored for thousands of years. While natural substances have historically been used to color most materials, these substances are often unable to permanently dye many types of materials. There is, therefore, a large demand for synthetic dye formulations that permanently color a material, including natural and artificial fibers, among many other beneficial uses. One of the largest markets for permanent dye formulations is the hair coloring market.
Hair is made of three layers: the outer layer called the cuticle, the sub-layer called the cortex, and an inner hollow shaft called the medulla. The cortex contains varying amounts of two natural color pigments, eumelanin and pheomelanin, that determine a person's hair color. Eumelanin is a dark pigment, and is responsible for brown and black color. Pheomelanin produces blonde and red. Thus the cortex of a black hair will contain densely packed granules of eumelanin pigment. An absence of pigment results in gray hair.
The permanency, or level of hair coloration, is dependent on the degree of penetration of colorant molecules into the hair. Temporary colorants merely coat the surface of the hair on the cuticle. Because the colorant does not penetrate the hair cuticle, it is easily washed out. Semi-permanent colorants, such as dyes, add color to the cuticle layer, but do not bind to the hair protein itself. When the hair is washed, the cuticle layer opens, allowing some color to escape.
To permanently change the color of hair, the coloring ingredients must be able to penetrate the outer layer of the hair called the cuticle, which consists of tightly packed, overlapping, colorless cells. Most permanent hair color products contain a developer and an alkalizing agent. The developer is usually an oxidizing agent such as hydrogen peroxide in water or a cream lotion, and the alkalizing agent is most often ammonia or ammonia substitutes such as organic amines. Alkalizing agents cause the hair to swell and thus allow the pigment to penetrate the hair cuticle deep enough to reach and replace the natural melanin.
To achieve hair coloring, both semi-permanent and permanent colorant formulations often involve the oxidation of toxic precursor molecules such as phenylenediamine or 2,5-diaminotoluene. Typical formulations involve hydrogen peroxide and ammonia, or even harsher chemicals such as lead acetate. Lead acetate is a neurotoxin that can be fatal if absorbed through the skin in high enough amounts. Several studies have suggested that the chemicals found in synthetic hair colorants, including ammonia, aromatic diamine color precursors, lead, organic solvents and coal tar derivatives, are either toxic or can have undesirable side-effects such as hair loss, burning, redness, itchy skin, swelling, or breathing trouble. Moreover, most hair coloring formulations employ oxidizing agents in high concentration. As a result, many people decide to forego hair colorants to avoid exposure to the chemicals found in the coloring compositions.
Although there are some natural formulations that employ compounds found in nature, they tend to be inconsistent and, often, provide only temporary results.
Some coloring processes can take upwards of 60 minutes to reach the desired level of coloration. To speed up the process metal ion catalysts can be used. The hair is either first treated with a metal ion composition followed by the color precursor materials or the hair is treated with a composition containing both the metal ions and the color precursor materials.
Most coloring processes rely on coloring the fibers, such as hair, to a particular pre-determined color such as brown, black, blonde, red, and various shades in between. There are no effective processes that are designed to return a person's hair to its original natural shade or a close proximity. In effect the pre-determined color process is a guess as to what the hair will look like when finally colored. Thus there is a long felt desire and need for hair coloring kits, compositions, processes and methods which will reproduce as closely as possible a person's hair to its original color and shade.
As a result, there is a continued need for coloring compositions that use natural compounds rather than synthetic or toxic chemicals to color hair permanently. Additionally, there is a continued demand for efficient and environmentally-friendly compositions and processes for coloring hair either permanently or semi-permanently that do not involve the use of organic solvents or organic bases. Further, there is a continued demand for hair dye formulations that use oxidizing agents in lower concentration.